Wet-pelletizing apparatus

ABSTRACT

Improved wet-pelletizing apparatus having an elongated conduit wherein a bed of wetted powder particles is agitated and tumbled to form pellets. The agitation is accomplished by rotating a coaxially extending shaft which carries a multiplicity of elongated members arranged in longitudinally spaced rows along the shaft and which extend outwardly therefrom toward the wall of the conduit. A stream of liquid-pelletizing medium is injected longitudinally into the conduit from an injector oriented to provide impact with a primary row of the members in which the number of members exceeds that in subsequent rows. Better atomization, and more quick and uniform distribution of the liquid throughout the powder bed, is thereby accomplished.

United States Patent inventor Richard E. Driscoll Monroe, La. Appl. No.887,031 Filed Dec. 22, 1969 Patented July 20, 1971 Assignee CitiesService Company New York, N.Y.

WET-PELLETIZING APPARATUS Primary Examiner.l. Spencer OverholserAssistant Examiner--R. L. Spicer, Jr. Attorney-J. Richard GeamanABSTRACT: Improved wet-pelletizing apparatus having an elongated conduitwherein a bed of wetted powder particles is agitated and tumbled to formpellets. The agitation is accomplished by rotating a coaxially extendingshaft which carries a multiplicity of elongated members arranged inlongitudinally spaced rows along the shaft and which extend outwardlytherefrom toward the wall of the conduit. A stream of liquidpelletizingmedium is injected longitudinally into the conduit from an injectororiented to provide impact with a primary row of the members in whichthe number of members exceeds that in subsequent rows. Betteratomization, and more quick and uniform distribution of the liquidthroughout the powder bed, is thereby accomplished.

PATENIEU JUL 20 m:

llIl I j I I 1 r c I c INVENTOR.

RICHD EDRISCOLL WET-PEELETIZING APPARATUS BACKGROUND OF THE INVENTIONMany powdered materials canbe wet pelletized in order to increase thebulk density of the materialwhile alsomaking it easier to handle in bulkform. This may be accomplished in-an elongated conduit into which thepowder and a pelletizing liquid are separately introduced and whereinthe wetted powder particles are agitated and tumbled to form-wetaggregates. Both the agitation and the tumbling can be achieved by meansof elongated members which are affixed to a rotating shaft and extendoutwardly therefrom. After formation, the wet aggregates are then driedto'produce dry pellets. In the past, the liquid-pelletizing medium hasbeen injected into the pelletizing conduit in a variety of ways fordistribution of the liquid over the powder particles, but it has beenrecently determined that directing a stream of the liquid longitudinallystream, and some of the liquid is thus conveyed upon the members intothe powder bed.

i It will be appreciated, therefore, that rapid uniform wetting of thepowder in the manner just described is dependent upon the frequency ofimpacts between the elongated-members and the stream of pelletizingliquid, and that this frequency is consequently dependent upon the speedat which the shaft is rotated. However, with any particular pelletizer,both the number of agitating members inthe longitudinally spaced rows,and the speed at which the shaft is rotated must be optimized to achievethe desired agitating and tumbling effects without exceeding thestructural limitations of the machine. In other words, satisfactorypelletization cannot be obtained if too many agitating members are usedin the longitudinally spaced rows, and the machine will-be damaged byvibration if the shaft is rotated at too high a speed. In many cases,each longitudinally spaced row of the members will contain only abouttwo to four members, and the shaft will be rotated at a relatively slowspeed, e.g. a few hundred r.p.m. As a result, atomization anddistribution of the liquid stream by impact with the rotating membershas not always been entirely satisfactory.

SUMMARY OF THEINVENT-ION It is therefore an object of this invention toprovide improved distribution of a liquid-pelletizing medium throughouta bed of powder that is agitated and-tumbled to form wet aggregates ofthe powder. Other objects and advantages .of the invention will becomeapparent from the following description thereof andthe appended claims.

By means of the present invention, wetted powder particles are agitatedand tumbled withinan elongated conduit to form wet aggregates of theparticles. For continuous operation, the conduit is provided with aninlet-opening at oneend for'the-introduction of powder at apreestablished rateand an outlet at the other end of the conduit for thedischarge of the wet aggregates. A rotatable shaft extends coaxiallythrough the con- 1 duit and a multiplicity of elongated members extendoutwardly from the shaft toward. the conduit wall. These members arearranged in longitudinally spaced rows along the shaft. In order toimprove atomization of the liquid-pelletizing medium and to assure quickand uniform distribution of the liquid throughout the powder bed, aninjector is employed which introduces a metered stream of the liquidinto the conduit in a substantially longitudinal directiomln conjunctionwith the injector, there exists a primary row ofelongated members whichextend outwardly from said shafLThisprimary row is located upstream ofsubsequent longitudinally spaced rows of the members, and the number ofmembers in the primary row is greater than the number of members insubsequent rows. Furthermore, the injector for the liquidstream isoriented toward the members of the primary row for impacting the liquidstream thereon during rotation of the shaft.

' Arranged thus, the liquid stream is disrupted more often duringrotation of the shaft, at any given speed, than would occur with anequal number or fewer members in the primary row than are employed inthe subsequent rows. Furthermore, since a greater number of members iswetted, the liquid is conveyed into the powder, upon the members, at afaster and more uniform rate. One advantage of the invention is theability to wet the powder particles quickly and uniformly even when therotational speed of the shaft is relatively low.

The number of members which can be arranged in the primary row isvariable, of course, and will depend among other things upon speed, orrange of speeds, at which the shaft is rotated. While in a typical casethe lateral spacing between the members in the primary row will besignificantly less than between members of the subsequent rows,sufficient lateral spacing to permit maximum contact between the powderparticles and the wetted surface of the members is generally desirable.

As an injector for the liquid-pelletizing medium, a liquid supplyconduit can extend transversally into the pelletizing conduit and can beprovided with at least one orifice for discharging the liquidlongitudinally into the pelletizing conduit. To additional advantage,this liquid supply conduit can be at least partially rotatable about itslongitudinal axis for controlling the angle at which the liquid streamis directed toward the elongated members of the primary row.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly insection, of one embodiment of the pelletizing apparatus of thisinvention.

FIG. 2 is a sectional view along the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary vertical side view, in section and somewhatenlarged, of the apparatus of FIG. 1 in the vicinity of line 2-2.

DESCRIPTION OF PREFERRED EMBODIMENT In 'FIG. 1, an elongated cylindricalpelletizing zone I is enclosed by the pelletizing conduit 2. The conduitis provided with an inlet 3 for introduction of powder at apreestablished rate, and a discharge outlet 4 for the removal of wetaggregates. A rotatable shaft 5 extends coaxially through the conduit 2.The shaft is mounted by means of bearings and seals 6 which are affixedto the end'closure plates 7 of the conduit. Elongated members, generallydepicted at 8, are affixed to the shaft 5 at their inner ends and extendoutwardly from the shaft toward the wall of the conduit 2. The elongatedmembers are arranged in longitudinally spaced rows'8a, 8b, 8c, 8d, etc.;along the shaft 5.

An injector assembly, generally depicted at 9, is employed forlongitudinal introduction of a liquid-pelletizing medium into thepelletizing zone. A liquid supply conduit'l0 extends transversally intothe pelletizing conduit 2 and is provided with'several orifices 11whereby streams 12 of the pelletizing liquid are introducedlongitudinally into the pelletizer and are directed'toward the plane ofrotation of the elongated membersin row 8a,i.e. the primaryrow.

To advantage, the liquid supply conduit 10 can be at least partiallyrotatable about its longitudinal axis to permit variation'of the angleat which the orifices l 1, and streams 12, are directed toward theelongated members in row 8a. A locking screw 13 extends through astationary bushing 14, and the screw can be tightened to secure theconduit 10 at a proper insertion depth and at the selected angularrelationship of the orifices II with row once the conduit 10 has beenpositioned. A packing gland, generally represented at 15, provides aseal between the pelletizing zone and the outside atmosphere.

As previously indicated, row 8a of the elongated members is regarded asthe primary row since the liquid streams 12 are directed toward it forimpact with the members therein and since the number of members isgreater than in subsequent rows. Atomization and distribution of theliquid is thus enhanced in the manner previously described. it can beseen in the drawings that row 8a contains eight elongated members, whilerows 8b, 8c, 8d, etc. seq. contain only two members.

It will be appreciated that rows which are considered to be subsequent,or following, with respect to the primary row are those which liedownstream therefrom in relation to the direction in which the powderbed travels through conduit 2 toward outlet 4. In the illustrated casethis direction of travel is from left to right, the primary row 8a beinglocated between the liquid injector and subsequent rows. It will beunderstood, however, that the primary row can instead be located to theother side of the conduit 10, and in which case the orifices 11 would bedirected in an upstream relation. With this altemative arrangement, theliquid injector is thus located between the primary row and thesubsequent rows.

In the drawings the elongated members 8 are all shown to besubstantially identical in shape, length and diameter, but it will beappreciated that this is not essential to the invention. The members ofthe primary row, particularly, can have dimensions quite different fromthose in the subsequent rows, the purpose being to further improveatomization and distribution of the pelletizing liquid.

Although the invention has been described with reference to a liquidinjector having several discharge orifices for eff cient distribution ofthe liquid over the members of the primary row, it will be understoodthat only one orifice need necessarily be employed, e. g. one whichprojects a sheetlike stream, or one which discharges droplets in acone-shaped pattern. Furthermore, the invention has also been describedwith reference to still other specific apparatus arrangements, and itwill also be understood that even other embodiments will become apparentwhich are within the spirit and scope of the invention as defined by theappended claims.

Therefore, what I claim is:

1. In a wet-pelletizing apparatus having:

an elongated pelletizing conduit wherein wetted powder particles areagitated and tumbled to form wet aggregates,

an inlet opening at one end of said conduit for the introduction ofpowder and an outlet at the other end for the removal of wet aggregates,

a rotatable shaft which extends through said conduit in coaxialrelationship therewith,

a multiplicity of elongated members arranged in longitudinally spacedrows along said shaft, said members extending outwardly from said shafttoward the wall of said conduit,

the improvement for enhancing atomization and uniform distribution ofaliquid-pelletizing medium throughout the powder which comprises:

a. an injector for introducing a stream ofliquid-pelletizing medium intosaid conduit in a substantially longitudinal direction,

b. a primary row ofelongatcd members which extend outwardly from saidshaft, the number of members in said primary row being greater than thenumber of members in subsequent rows, and wherein said injector isoriented toward the members of said primary row for impacting of theliquid stream thereon during rotation of said shaft.

2. The apparatus of claim 1 wherein said injector comprises a liquidsupply conduit which extends transversally into said pelletizingconduit, and at least one orifice for discharging the liquidlongitudinally into the pelletizing conduit.

3. The apparatus of claim 2 wherein said liquid supply conduit is atleast partially rotatable about its longitudinal axis.

4. The apparatus of claim I wherein said primary row of members islocated between said liquid injector and said subse uent rows ofmembers.

. The apparatus of claim 1 whereln said in ector IS located between saidprimary row and said subsequent rows of members.

1. In a wet-pelletizing apparatus having: an elongated pelletizingconduit wherein wetted powder particles are agitated and tumbled to formwet aggregates, an inlet opening at one end of said conduit for theintroduction of powder and an outlet at the other end for the removal oFwet aggregates, a rotatable shaft which extends through said conduit incoaxial relationship therewith, a multiplicity of elongated membersarranged in longitudinally spaced rows along said shaft, said membersextending outwardly from said shaft toward the wall of said conduit, theimprovement for enhancing atomization and uniform distribution of aliquid-pelletizing medium throughout the powder which comprises: a. aninjector for introducing a stream of liquid-pelletizing medium into saidconduit in a substantially longitudinal direction, b. a primary row ofelongated members which extend outwardly from said shaft, the number ofmembers in said primary row being greater than the number of members insubsequent rows, and wherein said injector is oriented toward themembers of said primary row for impacting of the liquid stream thereonduring rotation of said shaft.
 2. The apparatus of claim 1 wherein saidinjector comprises a liquid supply conduit which extends transversallyinto said pelletizing conduit, and at least one orifice for dischargingthe liquid longitudinally into the pelletizing conduit.
 3. The apparatusof claim 2 wherein said liquid supply conduit is at least partiallyrotatable about its longitudinal axis.
 4. The apparatus of claim 1wherein said primary row of members is located between said liquidinjector and said subsequent rows of members.
 5. The apparatus of claim1 wherein said injector is located between said primary row and saidsubsequent rows of members.